Morphological changes in starch grains after dehusking and grinding with stone tools

Area of Science:

• Archaeology
• Paleobotany
• Material Science

Background:

• Stone tools, including grinding slabs and mullers, offer insights into ancient subsistence strategies and plant food utilization.
• Analysis of residues on ancient tools reveals processing-induced damage, which can be understood through modern experimental replication.

Observation:

• Experiments were conducted using modern stone tools to dehusk and grind various millet species (Setaria italica, Panicum miliaceum, Setaira viridis).
• Residues from used and unused stone tool facets were analyzed for changes in starch grain morphology.

Findings:

• Dehusking millet did not significantly alter starch grain size or morphology.
• Grinding increased millet starch grain size by up to 1.2 times and caused surface damage and extinction cross distortion in approximately 25% of grains.

Implications:

• The observed changes in starch grains provide a new indicator for functional inference in grinding stone tool research.
• Distinguishing between de-husked and native millet starch grains remains a challenge for future research.